Shielded spark plug



Aug. 29, 1939. H, RABEzzANA SHIELDED SPARK PLUG Filed Dec. 27, 1938 ..1.VIIM

Snventor Patented Aug. 29, 1939 2,171,165

UNITED STATES PATENT GFFICE YSHIELDED SPARK PLUG Hector Rabezzana, Flint, Mich., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application December 27, 1938, Serial No. 247,741

4 Claims. (Cl. 12S-169) My invention relates to shielding means for ing the shield into the threaded opening referred spark plugs used with internal combustion'ento in an engine cylinder. gines to ignite the combustible mixture supplied The numeral Il designates an insulating memto the engine cylinder and the object thereof is ber made of a ceramic material, Bakelite, or to provide a hollow metallic shield, or can as equivalent substance and which has an annular it is sometimes called, associated with an interdepending skirt part l2 within the shield 5 which nal combustionA engine cylinder and which ensurrounds the upper end. of the plug 1; that is, closes and serves as a protector for a spark plug surrounds the upper end i3 oi the insulated elec- `of known and more or less conventional form; trede and the upper part of the insulating memlo in combination with a readily attachable and reber of the plug; and the dome-shaped upper part movable cap for closing the open end of the l5 of the insulating member il has a thin metalshield to thereby form a complete enclosure for a lic shell member l@ of like form which overlies spark plug contained therein. The usual insu-` the dome-like part and is secured in place therelated current supply lead is secured to and carupon by lugs il which are bent inward so as to l5 ried by said cap, and the act of placing the cap engage and lie beneath a circumferentially exl5 upon and removing it from the shield establishes tending ledge lil oi the insulating member. Said and interrupts a connection between the insumember has an annular groove i9 jwt within lated conductor of the supply cable through the shoulder tu which receives the upper end oi which current is supplied thereto and the insuthe shield 5 when the cap which comprises au lated electrode of the spark plug within said the insulating member li and its dome-shaped a a7 shield. shell member l@ is in place upon the shield; 0

In the drawing wherein the preferred embodiand said cap is held in place by resilient clips ment or" my invention is illustrated: 2d depending from the shell member i8 and Figure l is a view showing my improved spark which are arranged in alternation with the lugs plug shielding device in elevation. il as shown, and the lower ends of which lie 25 Figure 2 is a view showing the metallic shield within the groove i when the cap is in place closand the cap therefor upon a centrai vertical ing the upper end of the shield. The presence of plane indicated by the line 2 2, Figure i, a spark the tapered portion-Q and the fact that the hold.- plug and a supply conductor being shown in eleing clips are resilient permits the closing cap vation and member to be readily placed upon and removed 3g Figure 3 is a view showing various parts of the from the shield member Ei as will be understood. cap for closing the open upper end of the shield The insulating member il has a projecting and for securing the supply cable thereto in pertubular part or nipple 2l 'through which the supspective and separated from one another. ply cable 22 enters the shielding device, so that Referring now to the drawing, the numeral 5 the insulated conducting wire 23 thereor will 35 designates a hollow metallic shield tubular in come into contact with the upper end it oi the form and open at its upper end, and having a insulated electrode so as to supply current therethreaded extension 6 at its lower end adapted to to, the axis of said nipple being inclined relative screw into an interiorly threaded passage in an to the axis or" the shield so that the supply 4c engine cylinder, and which part 6 has a threaded cable will be disposed at an angle to the axis or" passage adapted to receive a spark plug 'l of the spari'- plug, as shown; and the numeral 2d known and conventional form; and which shield designates a lrnurled tubular securing member extends upwardly and encloses the plug l' which surrounds the nipple 2l, and has an inthroughout substantially the entire length therewardly extending ledge it which overlies a packof. The lower part of the shield therefore, in ing gasket 25 and compresses it against the end 45 the form oi shield shown, forms in eiect a bushoi said nipple to secure the supply cable 22 to ing for the spark plug; and the upper end therethe cap and to provide a tight joint between the of has a circumferentially extending groove 8 same and the cap. The insulating sheath of the for receiving the lower ends of resilient holding supply cable may have a circumferential groove ,0 members associated with the detachable cap 21 into which the gasket 26 is compressed to pro- 50 aforesaid. The upper end of the shield is tapered vide a stronger connection between the parts if as shown at 9 so as to facilitate the placing of friction alone is deemed inadequate to secure a the cap upon the upper end thereof, as will sufliciently strong connection between them. be understood; and an intermediate hexagonal The tubular securing member 24 is angularly part I0 is provided to receive a wrench for screwrotatable about the supply cable 22 and has a series of inclined lugs 2@ adapted to engage and interlock with stationary lugs 29 carried by an annular member 3d, which is secured to the shell membero i6 and surrounds an opening 3l in the wall thereof.

The supply cable 22 may therefore be secured to the cap by moving the tubular member 2Q to bring the lugs 23 into positions adjacent the lugs 29, the gasket 26 being meanwhile compressed against the insulating covering of the cable, and then rotating the member 2Q to bring the lugs 28 and 29 into interlocking engagement with one another.

The supply cable may obviously be disconnected from the cap without removing the cap from the tubular shield 5 by reversing the connecting steps above outlined. Ordinarily, however, the supply cable after laving been secured to the cap will remain connected therewith; and the cap as a whole, and the supply cable with it, will be lifted from the tubular shield if and when the supply cable has to be disconnected from the spark plug or when access has to be had to the spark plug which is housed within the tubular shield.

Having thus described and explained my inventinn, I claim and desire to secure by Letters Patent:

1. Spark plug shielding means comprising a hollow metallic shield tubular in form and open at its upper end, and having a circumferentially extending groove located adjacent said upper end; an insulating member supported upon the upper end of said shield and having a depending annular skirt part which surrounds the upper end of a spark plug .Within said shield, and the upper end of which member has a tubular nipple arranged at an angle to the axis of said shield; and a metallic shell member overlying the upper end of said insulating member and secured in place thereiipon by lugs of said shell which are bent into engagement with said insulating member, and which shell member has also resilient lugs depending therefrom and lower ends of which engage within the groove aforesaid of said shield. y 2. Spark plug shielding means comprising a hollow metallic shield tubular in form and open at its upper end; an insulating member supported upon the upper end of said shield and having a depending annular skirt part which surrounds the upper end of a spark plug within said shield, and the upper end of which member has a tubular nipple arranged at an angle to the axis of said shield; a metallic shell member overlying the upper end of said insulating member and secured in place thereupon by lugs of said shell which are bent so as to lie beneath a circumferentially extending ledge upon the periphery of said insulating member, and which shell member has also resilient lugs depending therefrom and the lower ends of which engage the periphery of said shield adjacent the upper end thereof; an angularly rotatable tubular member surrounding said nipple and having an inwardly extending ledge at its outer end, and a series of lugs at its inner end; and a series of lugs spaced about an opening in the wall of said shell member and with which said first mentioned lugs interlock when said tubular member is rotated.

3. Spark plug shielding means comprising a hollow metallic shield tubular in form and open at its upper end, and having a circumferentially extending groove located adjacent said upper end; an insulating member supported upon the upper end of said shield and having a depending annular skirt part which surrounds the upper'end of a spark plug within said shield, and the upper end of which member has a tubular nipple arranged at an angle to the axis of said shield; a metallic shell member overlying the upper end of said insulating member and secured in place thereupon by lugs of said shell which are bent into engagement with said insulating member, and which shell member has also resilient lugs depending therefrom and lower ends of which engage within the groove aforesaid of said shield; an angularly rotatable tubular member surrounding said nipple and having an inwardly extending ledge at its outer end, and a series of lugs at its inner end; a. gasket between said ledge and the outer end of said nipple; an annular member secured to said shell member and extending about an opening in the wall thereof; and a series of lugs carried by said annular member and with which said first mentioned lugs interlock when said t.;bular member is rotated.

4. Spark plug shielding means comprising a hollow metallic shield tubular in form and open at its upper end;l an insulating member supported upon the upper end of said shield and having a depending annular skirt part which surrounds the upper end of a spark plug within said shield, and the upper end of which member has a tubular nipple arranged at an angle to the axis of said shield; a metallic shell member overlying the upper end of said insulating member and secured in place thereupon by lugs of said shell which are bent into engagement with said insulating member, and which shell member has also resilient lugs depending therefrom and the lower ends of which engage the periphery of said shell adjacent the upper end thereof; and separable connecting means associated with said shell member for securing a supply cable in place within saidtubular nipple and for permitting said supply cable to be removed from said nipple.

HECTOR RABEZZANA. 

